Heat control system



De@ 9, 1941 K. c. BRowN ErAL 2,265,512

HEAT CONTROL SYSTEM Filed Oct. 13, 1938 Patented Dec. 9, 1941 HEAT CONTROL SYSTEM Kenneth C. Brown, Evanston, and Fredrlc Weyher, Chicago, Ill.; said Weyher assignor to said Brown Application October 13, 1938, Serial No. 234,752

4 Claims.

Our invention relates, genera1ly,.to electrical control systems. and it has particular relation to such systems employed for controlling the heat supplied to a building or th'e like in accordance with one or more variable temperatures, the combination of which determines the temperature of the building.

Inorder to control the temperature of a building, several factors involved should be considered. The object is not only to control temperature, but to control temperature most economically. Control systems may be designed to do a iine Job of controlling temperature, but they may at the same time cause the heating plant to operate iniemciently. The control system desired is one that will not only do a good Job in regulating temperature, but will also do it with a maximum degree oi!A efficiency.

The object of our invention, generally stated,

is to provide a heat control system which, after a shut down, will bring a heating plant up to maximum operating capacity independently of the main control means and will, after the warm-up period, permit the heating plant to be turned back over to be controlled by the main control means. Another object of our invention is` to provide such a heat control system, as set forth above, that is universal in application to any heating plant and building and adjustable to operate under substantially any given set of conditions.

Accordingly, our invention is disclosed in the embodiment hereof shown in the accompanying drawing, and it comprises th'e features of construction, combination of elements and arrangement of parts which will be exemplified in the system hereinafter set forth and the scope of the application of which will be indicated in the appended claims.

For a more complete understanding of the nature and scope of our invention, reference may be had to the following detailed description, taken in connection with the accompanying drawing, in which the single ngure illustrates diagrammatically one concrete embodiment of our invention.

Referring now to th'e drawing, it will be observed that the reference character III designates, generally, a boiler which is intended to be representative of any boiler that might be used for heating water and supplying it through a supply pipe il to a heating load such as ordinary hot water radiators. The heating water may be returned from the heating load to the boiler Il through a return pipe I2. The boiler Il may be Il, and natural draft alone or in combination with induced or forced draft may be used to obtain suillcient air supply. In addition to these provisions for air supply (not shown). an auxiliary blower I5 may be provided which can be driven by an electric motor Il. 'Ihe purpose of the blower II is to provide means for quickly forcing or bringing the boiler III up to its maximum capacity after a low or shut down period in -order that the heating system can be quickly brought up to its normal operating condition. The use of the blower Il in this connection will be more fully brought out below in connection with the description of the operation of our control system.

The stoker motor I4 and the blower motor Il may be connected for operation to a pair of energized conductors I1 through relays shown generally at I8 and Il, respectively. The energixed conductors l1 may supply the motors Il and Ii with 60-cycle, 1l0 volts, alternating current. The relays il and Il are provided with operating windings llw and Hw, respectively, which control the movement of contact members Il and Il. according to their degree of energiaation. A capacitor 20 is connected across the winding Ilw for preventing chattering of,the relay 2i. Th'e contact members 25 and 2l are indicated by full lines in the closed position, and are indicated by broken lines in the open position. In order that in normal operation only contact member 2l will be in the closed position, relay winding llw has a lower resistance than relay winding Itw.

With a view to controlling the energization of 35 relay windings ilw and iIw. they are connected in series circuit relation with each other and in series circuit relation with an electric valve shown generally at 21. The electric valve 'I1 is povided with a cathode llc, a control electrode or grid 21o, and an anode 21a. By varying the conductivity of the electric valve 21, it is possible to selectively control the operation of the relays Il and I0 to in turn effect the selective operation of motors Il and it for operating the stoker Il and the blower Il, respectively.

nred by a stokerv I3 driven by an electric motor 55 potential of the grid 21a relative to the cathode 21o, as will be hereinafter set forth, with the result that the conductivity of the electric valve 21 is varied accordingly, as is well known.

The Wheatstone bridge circuit 3|! is preferably energized with direct current. For this purpose, its terminals 3| and 32 are connected across a suitable direct current source. For example, in order to provide a suitable source of direct current a rectifier valve, shown generally at 33, may be provided, having an anode 33a, a cathode 33e, and a heating element 33h. Since the rectifier valve 33 is employed to provide half wave rectiiicationof alternating current, a capacitor 34 is connected between the terminals 3| and`32 in-` order to reduce the ripple of the rectified half waves.

A transformer, shown generally at 35, is provided for energizing the bridge circuit 30. rIt has a primary winding 35 that may be connected to any suitable source of alternatingcurrent, such as 60cycle,1110-volt source. The transformer 35 is also provided with secondary windings 31 and 38. As illustrated, the secondary winding 31 is employed for energizing the heater element 33h of the rectifier valve 33, while the secondary winding 33 provides the source of alternating current that is rectified for energization of the` bridge circuit 30.

Another transformer, shown generally at 45, is provided for energizing the relay windings |8w V"and |910, and for operating the electric valve 21. It has a primarywinding 4| that may be y connected to the same source of alternating current as the primary winding of transformer 35. Also, the transformer is provided with secondary windings 42 and 43. The secondary winding 42 serves to energize the cathode 21c, while the secondary winding 43 provides the operating potential for the plate circuit of the electric kvalve 21 and is connected to one terminal of the relay winding |8w of the relay I3. It will be observed that an adjustable resistor 44 and a capacitor 45 are connected to the secondary winding and to the grid 21g for modifying the triggerraction ofthe electric valve 21. The circuit for the grid 21g is completed by connecting the terminala of the Wheatstone bridge circuit 35 to a midpoint of the secondary winding 42.

As indicated hereinbefore, the conductivity of the' electric valve 21 is changed by varying the potential thatis applied to the grid 21g.y An increase in potential causes a decrease in conductivity and, vice versa, a decrease in potential causes an increase in conductivity. This is effected by varying the resistances of certainr of the arms A, B, C, and D of the Wheatstone bridge circuit.

Taking arms A, B, and D separately, arm A includes in parallel a temperature variable resistor 41 and a fixed resistor 48; arm B includes fixed resistors 43 and 50 and a temperature variable resistor 5|; and arm D includes an adjustable resistor 52 which is providedfor adjusting the firing point of the electric valve 21. The midpoint of arms A and C are joined by an adjustable resistor 53. By regulating the adjustable resistor 53 the relationship between the temperature variable resistors 41 and 5| may be varied as desired. Y

The temperature variable resistor 41 is placed outside of the building whose temperature is to be controlled. It maybe termed the outside unit and is preferably placed on theV north side of the and 45 into the arm A. When switch 54 is closed in the left hand position, temperature variable resistor 41 is cut into the arm A, and, when closed in the right hand position, fixed resistor 48 is cut into the arm A. A switch 55 is provided` for cutting in or out resistor 49.

Temperature variable resistor 5| of arm B is disposed in a suitable housing 55 through which the heated water from the boiler I0 flows. Re-

sistor 5| is so positioned that its temperature will be that of the water in the housing 55 and yet it is insulated therefrom in a suitable manner. Resistor 5| may be termed the boiler unit.

The resistor of arm B is connected in parallel with a mercury switch, shown generally at 51, and is shunted thereby when the mercury switch 51 is inthe closed position. The mercury switch 51 comprises a curved closed glass tube 58 with terminals 59 sealed in one end thereof and connected to binding posts 50 by a pair of flexible leads 6|. A pool of mercury 52 is sealed into the glass tube 58 and rests in either end of the glass tube 55, depending upon its position. The glass tube 58 may be carried by a clip from the center end of a metallic spiral 53. The metallic spiral 53 is fastened to the return pipe I2 at 54 and is in heat conductive relation therewith. If theY return Vpipe |2 is lagged, part of the lagging is removed in order that the spiral 53 may be installed. It will be seen that when the return pipe l2 is hot due to the temperature of the return water therein, the spiral 53 will the spiral 53 will then close up again. Normally,

the mercury pool 62 will be inthe right end of the glass tube 55 and the mercury switch will be in the open position. However, whenthe return pipe cools and the spiral 53 contracts sumciently, the` glass tube will become tilted to the left far enough to allow the pool of mercury 52 to pass over the curvel in the glass tube and to iiow into the left end thereof, thereby immersing the terminals 59 and closing the mercury switch 51.

Because of the curve in the glass tube 55 over which the mercury pool 52 must iiow, snap- A action will be obtained.

In describingV the operation of our control system, for making it more fully understood, it may` be assumed to be controlling the temperature of the building on a normal winter day. Under such conditions switch 54 will be closed in its left hand position, switch 55 will be closed, and the mercury switch 51 will be in the open position. The resistance of the temperature variable resistor 41, i. e., the outside unit, will be of such a value that the resistance of the temperature of variable resistor 5|, i. e., the boiler unit, will be large enough so that the temperature of the water flowing through the housing 55 will have to be high enough to maintain the building at a predetermined temperature level. The conductivity of the electric valve 21 corresponding to these conditions will be of such a value as to energize relay winding |8w suiiicientlyso that Ythe contact member 25 will be in the closed position, thereby completing the circuit to the motorl|4 and causing it to drive the stoker |3. However, the conductivity of the electric valve 21 will not be great enough to energize the relay winding |9w sufliciently so that contact member 25 will be in the closed position. If, now, the outside temperature rises sumciently, the resistance of building.` A two-way switch, shown generallyat 75 the temperature variable resistor 41, i. e., outside unit, will increase, and this increase must be balanced by a corresponding decrease in the resistance of the temperature variable resistor I, i. e., boiler unit, and, accordingly, a decrease in the temperature of the hot water going through the housing 56 will be called i'or. At this same time, the conductivity of the electric valve 2l will decrease due to the increase in the potential on the grid 21o', as is well understood. Ii the conductivity of the electric valve 2l falls enough, the relay I8 will open and the motor I4 driving the stoker I3 will be shut oil, thus stopping the fuel supply for heating water. Whenever the temperature o! the heating water flowing through the housing 56 drops below the level which corresponds to a certain outside temperature, the conditions in the bridge circuit 30 will change due to the change brought about in the resistance of the boiler unit 5I and the potentialvunder the grid 21g will be decreased, thereby causing an increase in the conductivity of the electric valve 21. 'Ihis increase in conductivity will permit the relay I8 to close, thereby starting up the stoker I3 again and causing more heat to be supplied to the heating water. It will be understood that the stoker I3 might be driven by a variable speed motor which might be made responsive to the conductivity of the electric valve 21, thus permitting a closer heat control to the heating water.

'Ihe above outlined daytime operations will be maintained as long as such temperature control is desired. However, in many buildings, as, for instance, apartment and omce buildings, it is not necessary to maintain as high a temperature level at night as that required'in daytime. Accordingly, this fact is usually taken advantage of to eil'ect a saving in fuel. Our temperature control system is provided for` shifting from daytime operation to nighttime operation. By opening the switch 55 it will be seen that the resistor 49 is cut in and, in order for the arm B to maintain its usual resistance, the resistance value of the boiler unit 5I must decrease accordingly. A demand for a lower resistance value of the boiler unit 5I means that a lower temperature of theheating water flowing through the housing 53 will be required. 'I'he switch 55 may thus be called a day-night` switch. When our system is operating under night conditions the stoker I3 will run less often than in the daytime, or, if it were variably speed driven, it would run slower.

During the latter part `oi' the night shutdown or low period-for example, about six oclock in the morning--the boiler I3 will have reached a low point in operation. At about this period the building will soon have to be at the customary daytime temperature level. If the temperature were to be raised to this level under the control of the main part of our control system, hereinbefore described in connection with day and night operation, it would require much too long a period. Accordingly, we have provided the mercury switch 51 responsive to the temperature of the return water in the return pipe I2 which, when in the closed position, shunts or cuts out resistor 50 in the arm B. This unbalances the bridge circuit 30 to a much greater degree than the normal operating changes, and allows the conductivity of the electric valve 21 to rise to such a value that both relays I8 and I9 are in the closed positions. Accordingly1 both the stoker I3 and the blower I5 will be put into operation,

vtut; to the openmosmon, thereby decreasing the conductivity of the electric valve 21, resulting in movement of contact member 26 to the open position and causing the blower I5 to be` shut down. After the mercury switch i1 is open, the boiler I0 will again be under the control of the main control system as described hereinbefore. By bringing the boiler I0 up to its maximum capacity is meant bringing it up to the limit allowed for by a pressure release valve or other safety device with which boilers are usually required to be provided.

It will be seen that this secondary control feature which brings the boiler III up to its maximum irrespective of the normal control system is especially important in spring and fall when the outdoor temperature approaches that at which no heat, or very little, is required for heating a building. This is due to the fact that during these periods the relationship between the temperature variable resistors 41 and 5I ls such that only a small amount of heat is required and the operation of the boiler I0 will accordingly be correspondingly slowly increased, whereas in winter time, when this relation is changed, i. e., a greater diierential between outdoor and building temperatures exists, the boiler III is brought up fromvshut-down operation to daytime operation at a greater rate.

In the summer time when the boiler I0 is used .l only for lheating hot tap water and not for heatv temperature variable resistor 5I only. 'I'he vtwoway switch 54 may accordingly be called a winter-summer switch.

As an alternative to having the relay I! connected to control the blower motor I6, it may be adapted to cut an auxiliary boiler into the supply pipe Il when the heat demand is sumcient to cause the relay I! to be closed.

It will be readily understood that our control system may be used in conjunction with steam heating systems and oil burners, powdered coal burners, and other types of heating plants.

Since certain changes may be made in the foregoing system and different embodiments of the invention may be made without departing from the scope thereof. it is intended that all matter contained in the foregoing description or shown in the accompanying drawing shall be interpreted as illustrative. and not in a limiting sense.

We claim as our invention:

1. The combination with a heat supply system for a building comprising, in combination, a heat source with a return line thereto and means forv regulating the heat supplied by said heat source, of control means for said heat regulating means responsive to the conductivity of an electric valve, and a bridge circuit, the grid oi said/electric valve being connected to one terminal of said bridge circuit, said bridge circuit including a temperature variable resistor responsive to outside temperature, a temperature variable resistor responsive to the temperature of the heating medium in saidheat source, and a mercury switch .tilted to the oi! or `on position in response to variable resistor responsive to outside temperature and said temperature variable resistor responsive tothe temperature of the heatingl medium in'said heat source `and of the position of said mercury switch.

2. In a system for controlling the heat supplied to a heated structure f from a source provided with heating fluid supply and return conduits and with diierenttemperature control means each energized through a. diierent electric switch, the combination of an electron tube provided with an input circuit and with an output circuit including means for causing said switches tobe operated in sequence in response todiilerent values of current in said output circuit, means including av bridge circuit for applying to said input circuit a resultant potential responsive to a temperature outside said structure and to the heating iluid temperatures in said supply and return conduits for selectively energizinggone of said temperature control means only when the heating iluid temperature in said return conduit has decreased to a predetermined value.

3. In a system for controlling the heat supplied to a heated structure from a source provided with heating iluid supply'and return conduits and with different temperature control means each energized through a different electric switch, the combination'oi an electron tube provided with an input circuit and with an output circuit including means for causing 4said switches to be operated in sequence in response to diierent values o1' current in said output circuit. means including Va bridge circuit for applying to said input circuit a resultant potential responsive to a temperature outside said structure and to the heating fluid temperatures in said supply and return conduits for selectively energizing one of said temperature control means only when the heating iiuid temperature in said return conduit has decreased to a .predetermined value, and means for rendering said system unresponsive to said outside temperature.

4. In a system for controlling the heat supplied to a heated structure from a source provided with heating fluid supply and return conduits 'and with different temperature control means each energized through a different electric switch, the combination of an electron tube provided with an input circuit and with an output circuit including means for causing saidswitches to be operated in sequence in response to diierent values oi current in said output circuit, means including a bridge circuit for applying to said input circuit a resultant potential responsive to atemperature outside said structure and to the heating fluid temperatures in said supply and return conduits for selectively energizing one of said temperature control means only when the the heating fluid temperature in said return conduityhas decreased to a predetermined value, and means for adjusting the Vrelation between the control eiects of said' outside and supply conduit heating uid temperatures. 

